1. Field of the Invention
The present invention relates to an optical ophthalmic treatment apparatus and, more specifically, to an optical ophthalmic treatment apparatus capable of selectively projecting an incisive YAG (yttrium-aluminum-garnet) laser beam to be used principally for the treatment of the front portion of the eye or a coagulative semiconductor laser beam to be used principally for the treatment of the fundus of the eye.
2. Description of the Prior Art
A known optical ophthalmic treatment apparatus irradiates the affected part of the eye with a therapeutic light beam, while the operator observes the eye illuminated by a slit lamp through a stereomicroscopic observation optical system. Some optical ophthalmic treatment apparatus uses an incisive YAG laser beam principally for the treatment of the front portion of the eye and other optical ophthalmic treatment apparatus uses a coagulative laser beam, such as argon laser beam or a semiconductor laser beam, principally for the treatment of the fundus.
FIG. 4 shows a previously proposed optical ophthalmic treatment apparatus capable of selectively using an incisive laser beam or a coagulative laser beam. As shown in FIG. 4, a YAG laser beam Ly and an argon laser beam La are guided, respectively, by separate half mirrors 52 and 53 to the light path of an observation optical system. When using the argon laser beam La, an illuminating light beam Ls is guided to the light path of the observation optical system and the components of the illuminating optical system including prisms are arranged on the side of the operator's eye E with respect to an objective lens 54 to avoid the interference of the components of the illuminating optical system with the argon laser beam La. Thus, the argon laser beam, i.e., a coagulative laser beam, is transmitted through the slit lamp optical system and the YAG laser beam, i.e., an incisive laser beam, is transmitted through the observation optical system. In FIG. 4, indicated at Lh is a collimating He--Ne laser beam projected together with the YAG laser beam Ly.
FIG. 5 shows another previously proposed optical ophthalmic treatment apparatus. As shown in FIG. 5, an incisive YAG laser beam Ly projected by a YAG laser 70 is expanded by a beam expanding concave lens 71, the expanded YAG laser beam Ly is reflected by the reflecting surface 67b of a laser beam reflecting prism 67 and collimated by a relay lens 68, the collimated YAG laser beam Ly is reflected by the reflecting surface of a laser beam reflecting mirror 62 so as to travel along the light path of an observation optical system, and then the YAG laser beam Ly is focused on an affected part of the patient's eye E. An illuminating prism 72 for reflecting an illuminating light beam Ls emitted by a slit lamp toward the patient's eye E is shifted to a position where the illuminating prism 72 will not obstruct the YAG laser beam Ly. A collimating He-Ne laser beam Lh for collimating the YAG laser beam Ly relative to the affected part is emitted by a He--Ne laser, not shown, and the He--Ne laser beam Lh is transmitted through an optical fiber cable 69 to the reflecting surface 67a of a laser beam reflecting prism 67. Then, the He--Ne laser beam Lh is reflected by the reflecting surface 67a so as to travel in parallel to the light path of the YAG laser beam Ly. A coagulative argon laser beam La emitted by an argon laser, not shown, is transmitted through an optical fiber cable 63, condensed by a lens 64, reflected by a movable mirror 65, condensed further and focused on the laser beam reflecting prism 67 by a lens 66 and travels along the light path of the He--Ne laser beam Lh.
In these two prior art optical ophthalmic treatment apparatus, the argon laser beam and the YAG laser beam travel along the same light path into the observation optical system at a position on the side of the operator with respect to the slit reflecting prism and the objective lens of the observation optical system.
In the former prior art optical ophthalmic treatment apparatus, which transmits the coagulative laser beam through the slit lamp optical system, the optical system for the coagulative laser beam turns together with the slit lamp optical system, which makes the observation of the illuminated part difficult.
In the latter prior art optical ophthalmic treatment apparatus needs a complex optical system for coaxially guiding the laser beam and the illuminating light differing from each other in wavelength. Furthermore, since the therapeutic laser beam is introduced into the observation optical system into the observation optical system through a position on the side of the operator with respect to the slit reflecting prism, the slit reflecting prism must be located outside the light path of the illuminating light.